Internal combustion engines need a torque transmission system by belt to activate alternators, water pump, air compressors and other accessories of the engine, as well as toothed belts to activate camshafts, injector pump and water pump.
Belt systems require adjustments during the operation of the engine to compensate slack and wear of the belt and other elements of the system, thus maintaining the tension of the belt under ideal levels to avoid loss of transmission, as well as the noise generated by the belt when sliding.
The compensation of belt slack or wear may be made by means of a manual or automatic tensioner. Automatic tensioners have technical advantages over the manual ones, but they are more complex and more costly.
Combustion engines are characterized by operating under an irregular rotation grade, which varies with the number of cylinders and driving wheel inertia. Such grade of irregularity is deleterious to various subsystems in the engine, such as the belt activation system. The working life of said automatic tensioners is limited due to this irregularity grade, as well as due to torque oscillations as required by accessories. The automatic tensioner works permanently.
Tensioners are applied to practically all vehicles having combustion engines, wherein the vast majority of models are automatic.
Conventional tensioners are composed by a base fixed to the engine block, hinged arm, spring and a dampening bush.
The automatic belt tensioner has the primary function to compensate the slack and wear of the belt and other elements of the system, by keeping the tension of the belt constant. The effect of the tensioner is the increased working life of the belt and the reduction of noise, besides allowing the extraction of better torque from the system.
Automobile industry sectors are increasingly requiring products having longer working life at lower prices from their suppliers. Therefore, there is an increasingly competition for new technology to stay competitive in the market.
State of the Art and Presented Defects
Automatic tensioners using springs to keep the tension under practically constant levels are already known in the market, as well as plastic dampening bushes, which generate friction with the hinged arm, reducing vibrations and oscillations of the system.
The dampening bush, since it works by the friction principle, has the inherent characteristic of wearing, limiting the working life of the product.
The spring generates torque at the hinged arm in the direction of the belt, but also generates a side effect which is crosswise torque, causing the tensioner to become misaligned. Said misalignment increases with bush wearing and, when combined with the effort of the spring, generates noise on the belt.
Another problem as presented is the difficulty or impossibility to do the maintenance of such models.
The new system dismisses the use of springs and dampening bushes as applied in the current state of the art and offers a much simpler and more efficient solution to enhance the operation, facilitate the manufacture and assembly and reduce costs and noise.
Another competitive advantage is the simple maintenance of all components composing the tensioner, wherein the body and the arm are fixed by a retention ring allowing disassembling and replacing the rubber element in case of wearing failure.
Besides the improvements as mentioned, the dampening element solves the wearing failure problem as found in the current state of the art, by eliminating the friction of the dampening bush and the crosswise torque of the spring. The damping element generates unidirectional torque, eliminating the misalignment of the tensioner, and also dissipating the energy by hysteresis of the rubber, generating only moderate heating, within admissible limits for the rubber compound as used.